Ok, new NUCs might be a bit expensive. But I can get lenovo tiny m72 or something like that, with core i3, 4GB of ram and 320gb hdd for <70usd. I would assume 4 of those are going to be similar in terms of size as turingpi build, much more powerfull and consume just a bit of power more (have a few similar machines, they consume something like 10W unless under heavy load)